Electrical gauge



@CL 10, 1944. G GARVlN ZJZl ELECTRICAL GAUGE Filed March 24, 1943 EE E IN V EN TOR.

Patented Oct. 10, 1944 UNITED STATES iiTENT OFECE l2 Claims.

This invention relates to improvements in electrical gauges, such as comparators.

The primary object is to provide a device of this character which is simple in construction, sensitive, accurate, and comparatively inexpensive.

A further object is to provide a device of this character utilizing variations in an iron-closed alternating current coil produced by shifting a movable armature by means of a touching pin, to vary the current flow in a circuit including a rectier in series therewith, and a measuring instrument connected with said rectier.

A further object is to provide a device of this character wherein a condenser is employed to increase the sensitivity of the instrument.

A further object is to provide a device of this character with novel electrical means for adjusting the calibration thereof.

A further object is to provide a device of this character with novel electrical means for zeroadjustment of the device.

A Afurther object is to provide a device of this character having a choke-coil-controlled circuit including a rectiiier, and a zero-adjustment circuit for applying to a measuring instrument connected with said rectifier a rectified counter E. M. F. of selected value.

A further object is to provide a device of this character having a novel, simple and compact construction and relation of choke coil, touching pin, associated control elements and housing. A further object is to provide a device of this character wherein the choke coil, touching pin and associated elements are preassembled as a unit for easy, quick and simple introduction into and mounting within a housing therefor.

In the drawing- Fig. 1 is a diagrammatic view of the basic circuit utilized in the devi-ce.

Fig. 2 is a diagrammatic view of a, circuit including Calibrating means, Zero-adjustment means, and sensitivity increasing means.

Fig. 3 is a longitudinal sectional View taken on line 3--3 of Fig. 4, illustrating the construction of the touching unit.

Fig. 4 is a transverse sectional view taken on line 4-4 of Fig. 3.

Fig. 5 is a transverse sectional view taken on line 5-5 of Fig. 3.

Fig. 6 is an enlarged fragmentary detail sectional view.

Reierring to .the drawing, and particularly to Fig. l which illustrates the basic circuit utilized in the device, the numerals I0 and Il designate lines connected with a source of alternating current. A step-down transformer I2 has a primary coil I3 connected across lines Ill--I I', and a secondary coil I4. A conductor I5 connects one end of secondary coil I4 with a coil I6 wound around one leg of a laminated U-shaped stationary armature I1 with which is associated movable armature I8 normally spanning the ends of the legs of said first armature and adapted to be shifted into spaced relation by a touching pin 25. A conductor I9 connects coil IB with one A. C. terminal of a rectifier 20. Rectiiier 20 is of the full wave type. The other A. C. terminal of rectifier 20 is connected by conductor 2| with transformer secondary coil I4. A milliameter 22 is connected to the D. C. terminals of rectier 20 by conductors 23 and 24. Movable armature I8 is so connected with feeler pin 25 that deflection of said pin shifts the same away from stationary armature Ii thus decreasing the iiux, induction and counter E. M. F. of self-induction of the coil, with resultant change in the flow of current which is measured in the meter 22.- Meter 22 may be calibrated in terms of distance of deection or movement oi said touching pin. I have found that satisfactory results are obtained by using a transformer I2 having an output of approximately 10 volts, a coil I5 having a D. C. resistance of approximately 5000 ohms and a copper oxide full Wave rectifier 20.

In Fig. 2 is illustrated a circuit as above described in which certain added features are incorporated. In this circuit a condenser 26 is interposed in conductor I9 in series With and between coil Iu and rectier 20. I have found that when this condenser is properly selected with relation to coil I6, the sensitivity of the device is greatly increased. Thus the deiiection of the meter for a given spacing of movable armature I8 from armature I'I is much greater when condenser 26 is employed than when it is omitted. The sensitivity of the device is increased further by connecting a second condenser 2l in parallel with coil I6 and condenser 26 by means of conductors 23. I have found that condensers 26 and 21 having capacities of .25 and .l microfarad respecitively produce satisfactory results 'when used with a core I'I and a coil I6 having a D. C. resistance of approximately 5000 ohms.

Calibration adjusting means may be incorporated in the circuit in conductor 2l, and may comprise a variable resistance 29. Adjustment of the 7Aresistance Varies the deflection of meter 25 for any given spacing of armature I8 from armature I1, to permit adjustment of the circuit to `connected by conductors 34 with the A. C. terminals of a rectier 35. The positive D. C. terminal of rectifier 35 is connected by conductor 35 With lead 24 connected with the negative D. C. terminal of rectier 20. The negative D. C. terminal of rectifier 35 is connected by conductor 31 with lead 23 connected with the positive D. C. terminalv of rectier 26. A variable resistance 38 is interposed in conductor 31. B-y adjusting resistance 38, the current leakage of coil 6 can be accurately counterbalanced to insure positive and immediate return of the meter to Zero.

. The construction of the touching unit, i. e.,

coil, armature, touching pin, associated parts,

`and Vmounting therefor, is illustrated in Figs. 3 to 5. A rigid annular member 40 has a pair of diametrically opposed longitudinal grooves formed therein parallel to the axis thereof. A narrow, fiat, elongated lbase plate 4| has one endthereof fitting snugly in one of said grooves and is fiXedly secured to member 46 at 42. Plate 4| isof a thickness slightly less than the depth of the side walls of the groove receiving it, whereby itsfull outer surface is spaced from the aXis of member 40 a distance not greater than the outer radius of memb-er 40. The free end portion of the base plate 4|, from a point 43 spaced from member 46, is of reduced width. The laminated U-shaped armature Il is xedly mounted onthe reduced width portion of plate 4|, as by means of a clip 44 of U-section tting around said plate with its `base 45 secured to said plate and its arms 46 engaging and secured to opposite sides of said armature l1. The opposite legs of armature extend perpendicular to plate 4| and are of a length less than the diameter oi member 40. Coil |6 encircles one of said armature legs.

In outwardly spaced relation to armature l1, plate 4| is provided with an aperture in which is iXedly secured a reduced neck portion 4'! of ae rigid tubular member or sleeve 48 extending perpendicular to plate 4|. An elongated pin 25 is keyed to and slidable in sleeve 48. Pin 25 projects from the inner or free end of a sleeve 48 and terminates in a rounded end 49. AY circum- Vferential groove is formed in the projecting portion ofpin 25 and receives a split ring 56 normally spaced from the end of sleeve 48 but engageable therewith to prevent withdrawal of the pin from said sleeve in the direction of plate 4|. The outer end of pin 25 has a concentric threaded longi tiallly centered relative thereto, lever 56 is provided with an aperture or hole 58 which is countersunk at its outer end at 59. A spacer block 60 has a pin 6| projecting centrally from one end thereof and passing through a central aperture in laminated movable armature plate I8. The outer end of pin 6| is swaged at 62 to form a head rivetingsaid armature plate and spacer together. The op-posite end of spacer 60 has a rounded surface 63, and a pin 64 projects centrally therefrom. Pin 64 is of a diameter smaller than aperture 58 into which it projects. Consequently,'dunng assembly, the parts may be placed in operative re- A (lever 56 in the nature of a narrow, elongated, Y

flat plate similar to base plate 4I, has one end thereof seated in the other groove of member 40 and secured thereto at 51. Lever 56 is also of a thickness slightly less than the depth of the side walls of the groove receiving same. The faces of plate 4| and lever 56 lie in substantially parallelr planes. At a point opposite core |'l and substan- 75 lation, with plate I8 `bearing flat on the ends of the llegs of armature l1, with pin 64 in hole 58, and with plates 4| and 56 in normal and uneXed position, and solder 65 can then be applied at the countersunk mouth 59l of hole 58 Without disturbing said operative relation, for the purpose of securely anchoring spacer 6U to lever 56. The free outer end of lever 56 projects outwardly past the sleeve 46 and pin 25, and the ring 58 on pin 25 holds said pin adjacent the inner face of said lever.

The construction above described, including annular member 46, base plate 4|, lever 56, armatures and I8, coi-l i6, sleeve 48, and pin 25 (but not head 53) is preferably preassembled as a unit, with conductors l5 and I9 passing through the boreof annular member 40. This preformed unit is then inserted in a tubular housing 66 preferably having an inner diameter snugly and slidably receiving member 46. The unit is secured in operative position in the housing by` screws 61 securing the annular member 4|!.to the housing. Housing 66 has a hole 68 formed therein concentric with pin 25, through which touching head 53 may be inserted for threaded connection of its shank 52 with the bore of pin 25. When` operatively secured to pin 25,`only the rounded" end 54 of head 53 preferably projects from the housing. At a point intermediate hole 68 and annular member 46, the housing is provided with a screw threaded hole receiving a set screw 69 Set screw 69 constitutes'a mechanical (not shown) of a'ccmparator or other device for measuring external dimensions, as is well understood in the art, or may be mounted on a handle (not shown) and provided with an accurately machined Contact surface diametrically opposite the feeler pin hole 68 when internal dimensions.

The unit mounting of the device in its housing provides only a slight clearance between the opposite outer longitudinal edges of plate 4| and lever 56 and the inner periphery of tubular housing 66. only for accurate measurement of small deflections of the touching pin, usually not greatly exceeding .005 inch, this small clearance is ample. However, if greater clearance is desired, the same can be obtained by increasing the depth of the grooves in member 49, or by reducing the width of the portions of plate 46 and lever 56 which.

TAn air gap in the normal closed iron core |'|-!8 1s thus provided which reduces the magnetic eld i used for measuring Y However, since thel device is intended' or iiux and thereby alters the inductance in coil I6, so that by proper calibration of meter 22, the extent of movement of touching pin can be read upon said meter. Scale divisions on the meter may be in any suitable unit of length, depending upon the sensitivity of the meter and the circuit, and upon the desired full scale range of measurement.

I claim:

l. An electrical gauge comp-rising a tubular housing having an opening therein, an annular member secured in one end of said housing, a pair of spaced parallel elongated bars each secured at one end to said annular member, an iron core carried by one bar, a coil encircling a portion of said core, an armature carried by the other bar and normally engaging said core, a sleeve carried by the outer ond of said iirst bar, and a pin slidably mounted in said sleeve to bear against the opposite bar at one end, the other end of said pin projecting through said housing opening.

2. An electric gauge comprising a rigid annulus, having opposed longitudinal grooves, a pair of spaced elongated bars each secured at one end in one of said grooves, a core carried by one bar spaced from said annulus, a coil encircling a portion of said core, a rigid guide carried by the outer end of said bar, an armature carried by the other bar in cooperative relation to said core, and a pin shiftably carried by said guide and engageable with said last named bar.

3. An electric gauge as deiined in claim 2 wherein said parts constitute a preformed unit, and a housing for said unit having a tubular portion snugly receiving said annulus.

4. An electric gauge comprising a rigid support, an elongated bar secured at one end to said support, a core mounted on said bar, a coil encircling at least a portion of said core, a rigid guide carried by the free end portion of said bar and extending transversely thereof, an elongated resilient arm secured at one end to said support and extending in spaced relation to said bar, an armature carried by said arm in cooperating relation to said core, and a pin slidably carried by said guide and engageable with the free end of said arm.

5. An electrical gauge comprising a pair of spaced elongated bars, bar mounting means interposed between said bars at one end thereof, a core positioned between said bars and carried by one bar, a coil encircling at least a portion of said core, a. transverse guide positioned between said bars and carried by the free end portion of said last named bar, a pin slidable in said guide and engageable with the other bar at one end and projecting laterally outwardly from said iirst bar at its opposite end, an armature carried by the other bar in cooperative relation to the core, a housing having an opening receiving the laterally projecting end of said pin, and means securing said mounting means to said housing.

6. An electrical gauge comprising a pair of elongated bars, means secured to said bars at one end thereof to mount said bars in spaced relation, a core carried by the inner face of one bar, a coil at least partially encircling said core, a transverse guide carried by the inner face of said last, named bar, a. pin slidably carried by Cil said guide with ones of its ends projecting laterally outwardly from said last named bar and the other end engaging the other bar, an armature cooperating with said core, a mounting member secured to said armature and including a pin, the other bar having an opening in which said last named pin fits loosely, and solder in said opening encircling said last named '7. An electrical gauge comprising a mounting member, an elongated bar secured at one end to said member, a guide carried by the free end of said bar and extending perpendicular thereto, a pin slidably mounted by said guide, a retainer on said pin engageable with said guide to limit movement of said pin in one direction, a core carried by said bar adjacent said guide, a coil encircling a. portion of said core, a second bar secured at one end to said member and extending in spaced relation to said iirst bar and engageable by said pin, and an armature carried by said second bar and cooperating with said core.

8. An electrical gauge comprising a housing, a mounting member secured in said housing, a pair of spaced elongated bars each secured at one end to said mounting, an inductance unit carried by one bar and including an armature carried by the other bar, and means slidably carried by the free end of one bar and engageable with the other bar for laterally delecting the latter, said housing having an opening through which said deecting means projects.

9. An electrical gauge as dened in claim 8 wherein said deecting means includes a portion positioned between said bars and a projecting portion detachably connected therewith.

10. An electrical gauge comprising a mounting member, a pair of elongated bars each secured at one end to said mounting member in spaced relation, a variable inductance unit having cooperating parts carried by opposite bars, deflecting means slidably carried by one bar and engageable with the other bar, said member, bars, inductance unit and deflecting means constituting a unit, a housing receiving said unit and iixedly supporting said mounting member, and a contact member projecting from said housing and detachably connected to said deflecting means.

11. An electrical gauge comprising a rigid mounting member, a pair of spaced bars each secured at one end to said mounting, a variable inductance unit having cooperating parts carried by opposite bars, deflecting means slidably mounted on one bar and engageable with the other bar, and a housing having a portion fitting around said mounting, and an opening through which a portion of said deflecting means projects.

12. An electrical gauge comprising a rigid mounting member, a pair of spaced bars each secured at one end to said mounting, a variable inductance unit having cooperating parts carried by opposite bars, deiiecting means slidably mounted on one bar and engageable with the other bar, a housing having a portion iitting around said mounting and an opening through which said deflecting means projects, and means for adjusting the position of said bars in said housing,

GEORGE L. GARVIN. 

